In some instances a cushion or pad is used to provide comfortable support for a person who is undergoing a medical procedure which may include imaging. Such a pad typically is generally planar and made from polymeric foam material of substantially uniform thickness. The length and width of such a pad normally are much greater than its thickness. Such a pad often is provided with an outer, skin-like protective coating formed by the application to the exterior of the pad of one or more coats of liquid paint-like material which then is permitted to dry or cure. Typically, such liquid coatings shrink in response to drying or curing and impose forces on the pad that compress it in all directions. It is the nature of such liquid coatings that, even when applied to a pad with great care, the shrinkage and corresponding compression are variable and unpredictable, thereby resulting in the production of a pad whose dimensions are not acceptable.
Typically, it is required that a cushioning or positioning pad fit a medical table or other patient support on which it is used and within certain dimensional tolerances. This usually means that the length and width of the pad must be controlled closely. It is desirable, therefore, to stabilize these dimensions during fabrication and coating so that variable shrinkage does not result in an unacceptable dimensional change. However, the means by which dimensional stabilization is achieved should not unduly stiffen the pad in the thickness dimension and thereby prevent the pad from providing comfortable support for a person.
In other instances a cushioning or positioning pad is required to support a person in a fixed position, or in an anatomical configuration required for a specific medical procedure. Such a positioning device may have any one of a variety of different shapes as may be required by the procedure in connection with which it is used. The shape of a positioning pad therefore may be geometrically complex. The most commonly used means for shaping such pads includes costly equipment or tooling which causes the cost of such pads to be inordinately expensive if the expense of the required shaping equipment or tooling must be amortized over a small production volume. It is desirable, therefore, to provide relatively inexpensive means of accomplishing the necessary shaping of the pad.
In still other instances it is desirable that a cushioning or positioning pad made of resiliently deformable polymeric foam, which naturally has isotropic mechanical properties, be modified for an application other than those referred to above so that the mechanical properties of such pads are anisotropic for all or a portion thereof. For example, the modified pad might be required to respond to the application of certain mechanical loads or external influences in one manner, and to respond to the application of other loads or influences applied at a different location in another manner.